Connecting classification with phylogeny

Connecting classification with phylogeny

Using phylogeny to trace the relatives of birds

Each tree is a hypothesis about the most likely path of evolution based on the data available

Anatomy of a phylogenetic tree

How to draw phylogenies: branch shape and length

How to draw phylogenies: branch shape and length

Mapping traits on a (review homology)







  • Critical innovations: Derived traits
    • adaptive traits that define new taxa
    • marked with ‘slashes’ on tree
    • ‘shared derived character’ in book
    • evolutionary novelties


  • Shared ancestal traits:

Convergent evolution in marine mammals (analogous traits)

How to use derived characters to infer phylogeny

Let’s draw it





  • Parsimony = Simplest solution is the likely path of evolution


  • A logical way to identify homologous and analogous traits


  • Minimize the # of evolutionary changes needed to explain your character data

How to draw a phylogeny…

Whale Evolution: A Case History



  • Phylogenetic trees based on morphology place whales outside of the artiodactyl group


  • Atiodactyl: mammals - cows, deer and hippos
    • hooves, even number of toes
    • unusual pulley-shaped ankle bone


  • Astragalus ankle bone is a shared derived trait for all artiodactyls

Whale Evolution: A Case History



  • How do we determine evol’n relationships?
    • morphology - presence/absence of weird ankle bone
    • DNA sequences - shared gene families


  • Depends on what data you have!
    • poor fossil record


  • Molecular data suggests a closer relationship between whales and hippos…

Whale Evolution: Whales and Hippos share common ancestor